Group of lenses



ent part of" an ,opticalfde ipe, which is de- Patented Mar. 30, l1-926.; UNITED STATES y PATENT OFFICE.

n ANs BoEGEHoLD, oF JENA, GERMANY, AssIGNoRTo THE FIRM JENA, GERMANY. i

OF CARL ZEISS, 0F

.Application led August 1921. serial No. 490,725.

(GRANTED UNDER THE rnovIsIoNs or THE AcT or MARCH s, 1921, 41 sTAT. L., 1313,)

Taal] whom t may cantera.:

Be itlmown that 1, )HANS BOEoEHoLD, a citizen of the GermaniEmpire, residing at Jena, Germany, have-invented a new and 'useful Group of Lenses (for which I have filed an application in ermany, August 31, '1918 Austria, May 29, 920; England, June 14, 1920, Patent No. 145f,023;',1tal June 28, 1920; and France, JulylI 9,1920, Patent No. 519,981), of which the ,olloyving is a specifi' cation. g

The present invention relates to a constitutely reduced phosigned for producing mi writings, with a tographs, for instance view to having these p"o,tographs of writings Vdispatched by carrier-pigeons.` If, on employing such a device, it be desired to avoid an inconveniently great distance of the object to. be taken, it. will be lfound neces- Vsary to arrange for a small focal length of the device, but at the Asame time the aperture must belarge, so that the definitionof the image is not impaired by way of diffraction. These requirements are best complied with, in case the-desired reduction is so great that a'device of' thetype of a photographic objective is out of the uestion, by la :device which is'of the type o a compound micro-v scope but is used in such a position, in which that part which cri'responds in its construction to the objective of the microscopewis turned toWards't-he sensitized iilm, and'that part which corresponds in its construction to the ocular of the microscope faces the object to be taken. If, however, a microscope of `the ordinary type is employed', that is to say, one in which the ocular 4has a. collective keffect as well, larger objects cannotbe imaged satisfactorily because it will genervally be found4 impossibleto eliminate in a sufficient degree the astigmatism of oblique pencils and the chromatic difference of the magnification together with the curvature o f the image-field. The reason for this is, that, on employinga collective ocular of a microscope, it 1s not vvery well possibleto impart to the image rformed by this ocular such a curvature that a plane image of the said image would just be produced ,jbyf. the'ob jectiveoftl'iel microscope(4 According to the ,invention vthe last named problem may, however, be solved, if that group of lenses which is to be located to wards the object to be taken be so constructed as to be dispersive (which in ocu-4 lars for microscopes has hitherto already been practised in certain cases), whereby, however, this group should consist of two dispersive members separated from one another, each of'which. being composed of at least two lenses. As a matter of course the new groupof lenses may also be used in a, device acting in the reverse path 'of the rays, therefore, for

producing greatly enlarged photographs, or

for projecting under high magnification.

The annexed drawing shows a section y through a group of lenses\corresponding to the present invention in which each 'of vthe two dispersive members consists of two lenses' cemented together. A suitable collective system which according to the above explanation would, in addition, haveto -be .disposed behind this group, is shown by l'Meaatonement@ n millimeters,

The focal iength of this grup of lenses amounts to2(l,16 mm. Behind this group of lenses an apochromatic microscopeobjective having a"ffocal length of 16 mm. and

consisting o-s'ix lenses a, b, 0,. d, e 'and 'f isb located, of 'which the focal'point facing this group o-flenseshas a. distance .fromthe focal point ofthe group of dispersive lenses which faces the said focal "point amounting to about '.165 mm. The wholelarrangement will allow, forl'instance, .to fom'jan' image'in a plane of la plane object, which is situated`750 mm. away in front of l'che dispersive group of lenses, reduced six hundred times, without, on an angle of the field of View facingl the object and amounting to almost 30 being involved, a disturbing lack of definition becoming evident.

I claim: v An objective system for producing minutely reduced photographs, composed of a which the one is dispersive While the other i is collective, and a collective group, disposed behind the first-named group at n, distance 155 from it greater thanthe focal length of the collect-ive y group.

c HANS BOEGEHOLD. 

